Well, this amp was built in `96.
Nicely built, with 2 transformers, some Elnas and mostly ceramic caps.
I like how this amp sounds, but i think it can do better.
My first and obvious ideea is to change the 2 large reservoir caps. They`re 6800uF at 56V, a small to fair value I guess. Even my CDP has a larger reservoir cap ( 10.000 uF
). I have 2 Russian 15.000uF/80V caps next to me, doing nothing. But this is this enough ?
In the next part, I will remove those 2 ceramic caps at the CD-P input.
And afterwards, I dont know.
That`s we`re you guys come in. Help me improve this little beast.
Nicely built, with 2 transformers, some Elnas and mostly ceramic caps.
I like how this amp sounds, but i think it can do better.
My first and obvious ideea is to change the 2 large reservoir caps. They`re 6800uF at 56V, a small to fair value I guess. Even my CDP has a larger reservoir cap ( 10.000 uF
). I have 2 Russian 15.000uF/80V caps next to me, doing nothing. But this is this enough ? In the next part, I will remove those 2 ceramic caps at the CD-P input.
And afterwards, I dont know.
That`s we`re you guys come in. Help me improve this little beast.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
Good news:
Purchased 2x31000uF Sprague capacitors.
http://i26.tinypic.com/otho8y.jpg
http://i30.tinypic.com/10d5xms.jpg
Purchased 2x31000uF Sprague capacitors.
http://i26.tinypic.com/otho8y.jpg
http://i30.tinypic.com/10d5xms.jpg
Damn, cannot edit.
Measured the main transformer voltages.
~35,5V in IDLE
~35V in LOAD
And this gives us a theoretical voltage in VDc
~50,055V in IDLE
~49,35V in LOAD
If we include the diodes dropout (which i didnt calculate) i think (theoretical) we will have ~ 48V in LOAD.
Pretty close to my 2 Sprague capacitors.
What do you think ?
Measured the main transformer voltages.
~35,5V in IDLE
~35V in LOAD
And this gives us a theoretical voltage in VDc
~50,055V in IDLE
~49,35V in LOAD
If we include the diodes dropout (which i didnt calculate) i think (theoretical) we will have ~ 48V in LOAD.
Pretty close to my 2 Sprague capacitors.
What do you think ?
http://i32.tinypic.com/2rfpiqe.jpg - number 19
and those 2 chemis:
http://i26.tinypic.com/1sb6gk.jpg
number 14 and 15.
and those 2 chemis:
http://i26.tinypic.com/1sb6gk.jpg
number 14 and 15.
I`ve searched for parts that might be changed to gain some improvements.
The first thing, is the bridge rectifier. I might change this to four Schottkys and bypass them with 0,1uF ceramic. Before the bridge I`m thinking about putting some coils and 1Ohm resistors.
Next to the Power Transistors I`ve spotted some resistors that might be changed: 2x47O, 2x560, 2x47K, 2x100K, 2x6,8K, 4x5,6K. There are no pots. The collector-emitter Voltage might be changed by using another fixed resistor.
The Power Transistors are made by Sanken : 2SA1695/2SC4468.
The final Reservoir Caps are 2 Siemens AL-ELKO 17,000uF 75V.
The first thing, is the bridge rectifier. I might change this to four Schottkys and bypass them with 0,1uF ceramic. Before the bridge I`m thinking about putting some coils and 1Ohm resistors.
Next to the Power Transistors I`ve spotted some resistors that might be changed: 2x47O, 2x560, 2x47K, 2x100K, 2x6,8K, 4x5,6K. There are no pots. The collector-emitter Voltage might be changed by using another fixed resistor.
The Power Transistors are made by Sanken : 2SA1695/2SC4468.
The final Reservoir Caps are 2 Siemens AL-ELKO 17,000uF 75V.
OK, I received the caps yesterday. They are pretty heavy and bulky.
I focused my attention on the Amplifier CD Player Input.
2 Ceramic caps, 6 resistors, 2 electrolytics and one OPAMP (NJM2068).
The NJM is in SIL Package. Some Browndogs adaptors will fix this.
I am interested in changing this OPAMP.
I have the following at hand: OPA132, OPA2132, THS4032.
The CD Player is equipped with LT1361 which has a pretty high slew rate.
The CDP DC offset is low, 2-3mV, while the amplifier offset is 15mV (peak)
Here is the input PCB : http://www.uploadgeek.com/uploads456/0/P3106818.JPG
I focused my attention on the Amplifier CD Player Input.
2 Ceramic caps, 6 resistors, 2 electrolytics and one OPAMP (NJM2068).
The NJM is in SIL Package. Some Browndogs adaptors will fix this.
I am interested in changing this OPAMP.
I have the following at hand: OPA132, OPA2132, THS4032.
The CD Player is equipped with LT1361 which has a pretty high slew rate.
The CDP DC offset is low, 2-3mV, while the amplifier offset is 15mV (peak)
Here is the input PCB : http://www.uploadgeek.com/uploads456/0/P3106818.JPG
I just bought 5 SDT12S60 Rectifiers.
http://www.datasheetcatalog.org/datasheet/infineon/1-SDT12S60.pdf
The price was very good: 14 Euros ship. incl. to Romania.
http://www.datasheetcatalog.org/datasheet/infineon/1-SDT12S60.pdf
The price was very good: 14 Euros ship. incl. to Romania.
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